Is the oxygen atom of carbon monoxide coordinated to the copper of hemocyanin?

The carbon monoxide binding site of hemocyanins was studied by comparing the isotope shift of the CO-stretching frequencies in CO-hemocyanins with that of carbon monoxide diethylenetriaminecopper(I)tetraphenylboron in which the carbon atom of CO is coordinated to the copper. Coordination by the carbon atom of CO in CO-hemocyanin is suggested.     

Marginal Zinc Deficiency in Pregnant Rats Impairs Bone Matrix Formation and Bone Mineralization in Their Neonates

Zinc (Zn) deficiency during pregnancy may result in a variety of defects in the offspring. We evaluated the influence of marginal Zn deficiency during pregnancy on neonatal bone status. Nine-week-old male Sprague-Dawley rats were divided into two groups and fed AIN-93G-based experimental diets containing 35 mg Zn/kg (Zn adequately supplied, N) or 7 mg Zn/kg (low level of Zn, L) from 14-day preconception to 20 days of gestation, that is, 1 day before normal delivery. Neonates were delivered by cesarean section. Litter size and neonate weight were not different between the two groups. However, in the L-diet-fed dam group, bone matrix formation in isolated neonatal calvaria culture was clearly impaired and was not recovered by the addition of Zn into the culture media. Additionally, serum concentration of osteocalcin, as a bone formation parameter, was lower in neonates from the L-diet-fed dam group. Impaired bone mineralization was observed with a significantly lower content of phosphorus in neonate femurs from L-diet-fed dams compared with those from N-diet-fed dams. Moreover, Zn content in the femur and calvaria of neonates from the L-diet group was lower than that of the N-diet-fed group. In the marginally Zn-deficient dams, femoral Zn content, serum concentrations of Zn, and osteocalcin were reduced when compared with control dams. We conclude that maternal Zn deficiency causes impairment of bone matrix formation and bone mineralization in neonates, implying the importance of Zn intake during pregnancy for proper bone development of offspring.     

Syntheses and structural characterization of mononuclear Rh-Cp* and Ir-Cp* complexes with η-phenanthrene, η-pyrene and η-triphenylene

Four novel mononuclear Rh-Cp* and Ir-Cp* complexes with polycyclic aromatic hydrocarbons (PAHs), [M(Cp*)(η⁶-PAHs)](BF₄)₂ (M = Rh and Ir; Cp* = η⁵-C₅Me₅; PAHs = phenanthrene (phn), pyrene (pyr) and triphenylene (triph)), were prepared by the reactions of the intermediate [M(Cp*)(Me₂CO)₃]²⁺ with appreciable PAHs. Their structures were characterized by a single crystal X-ray analysis, ¹H, ¹³C {¹H} NMR and 2D NMR techniques. The X-ray crystallographic studies showed that the [M(Cp*)]²⁺ fragment is η⁶-coordinated to one terminal benzene ring in each PAH. In particular, it is interesting to note that the partial π/π/π/π interaction was formed in the Ir-pyr complex [Ir(Cp*)(η⁶-pyr)](BF₄)₂. The 1D and 2D NMR studies described that the Rh-Cp* and Ir-Cp* complexes with PAHs gave unique ¹H and ¹³C {¹H} NMR spectra with positive coordination shifts (Δδ(¹H, ¹³C)) in (CD₃)₂CO at 23 °C, which are likely induced by the local effect and the non-local effect on the coordination of the [M(Cp*)]²⁺ fragment to PAHs. The decreasing of the coupling constants (³J_H-H) in the η⁶-coordinated benzene ring is also induced, with no changes in the uncoordinated benzene rings. The time-course of ¹H NMR spectra showed that Rh-Cp* and Ir-Cp* complexes with PAHs are partially dissociated to [M(Cp*)(Me₂CO)₃]²⁺ and metal-free PAHs in (CD₃)₂CO at 23 °C. It was demonstrated that their stabilities are in the order of Ir-triph, Ir-phn, Ir-pyr and Rh-triph complexes in (CD₃)₂CO.